Glow discharge device



7 1935- H. H. GEFFCKEN ET AL 17,278

GLOW DISCHARGE DEVICE Filed Aug. 23, 1930 VENTORS v Helm/ch sf/cg en 1 Hans R. Rlchfek ATTORNEY Patented Oct. 15,1935

QLOW DISCHARGE DEVICE I Heinrich Gelflcken and Hans R. Richter, Leip- .zig, Germany, assignors, by mesne assignments,

to Radio Corporation of America; New York,

N. Y., a corporation of Delaware Application August as, 1930, Serial-No. 411,212 In Germany August 26, 1929.

11 Claims.- 176-122) Our invention relates to glow discharge devices and more particularly to glow tubes which substantially consist of a'vessel containing a, gaseous atmosphere and electrodes for applying an electric potential.

Elf a suitable electric voltage is applied to the electrodes of such a tube ionization of the gas molecules takes place whereby energy is liberated in the form of lightradiation. Tubes of this kind are extensively used for different pur- I poses, such as in luminous signs for advertising,

for recording pictures in picture telegraphy and television, and like purposes. The glow discharge device as described in our invention'is primarily intended for use in television systems, but-it is to be understood that its application broadly applies to any kind of glow discharge device used I in practice.

One object of our invention is to provide a new and improved glow discharge tube.

- Another object of our invention is to provide aglow discharge device with improved stabilization of the electric discharge. and which may be operated with lower voltages and smaller current densities as compared to devices of this kind now being used in the art.

. Another object of the invention is to provide novel means in connection with a glow discharge device whereby the glowing surface exhibits an improved uniformity of luminescence.

Still a further object of our invention is to provide a, novel glow discharge tube in which the cathode drop is considerably decreased and which accordingly may be operated with lower voltage as compared to the tubes hitherto known in the art.

A further object of the invention is to decrease the disintegration of the cathode electrode whereby thelife of the tube isincreased.

' Another object of our invention is to produce- 1 understood, however, that the description of the drawing should be illustrative only of the broad principle underlying our inventiomwhich is sub ject to many modifications all coming within its broad and most comprehensive scope, as ex- .pressed in the appended claims.

In the drawing:

Fig. 1 shows a front elevation of a glow dis- 5 charge device in accordance with our invention;

Fig. 2 is a side elevation of the device as shown in Fig. l; and

Fig. 3 shows in a schematic manner a television system in which our novel glow iamp has 10 been embodied.

Similar reference numerals refer to similar elements inboth figures of the drawing.-

As pointed out, our invention is primarily directed to a glow discharge lamp for television 15 purposes. As is well known in television, glow discharge tubes have been used with a flat cathode whose field of luminescence comprises the entire field of the picture and is viewed through a rotating spiral disc or another equivalent de- 20 vice. Therear side of the cathode is usually prevented from producing a glow discharge by providing it with a cover or coating it with a suitable material.

In accordance with our invention, weaprovide 2 a frame-like anode disposed in front of the operating surface of the cathode and circumscribing the field of vision. By this construction it is possible for the discharge tube to be operated with very low voltages, and, with compare.- 3 tively low operating currents, a uniform glow discharge covers the entire field of vision without. any tendency of flashing or ju'mping as is observed in the usual discharge devices used in I the art. Both effects are further increased if, 85 in place of a simple wire frame, a flat frame is used, which maybe obtained by punching from a sheet of metal or which may be comprised of fiat stripsof metal. This frame is disposed in front of the field of vision of the cathode. 40 This construction has the further advantage of a very sharp contour of the field of vision which allows an easy regulation and adjustment of the frequency and phase'of the televisor. This effect may be further ,increased by allowing the surface of the anode frame to protrude beyond the surface of the cathode in such a manner that even when viewing the cathode in an oblique direction only the field of vision as comprised by the anode frame will appearin high luminescence.

Referring to Fig. 1, we have'shown-a glass tube 1 or'bulb I which contains acathode 2 having the shape of a plate and mountedin anyone of the well-known manners (not shown in the drawing). The rear side of the cathode may be covered by mica or may be enameled or provided with any other suitable coating for preventing the production of the glow discharge thereon. We have shown the anode frame 3 having an opening substantially of the size of the image disposed in front of the cathode 2 in the direction of vision.

As seen from the figure, the anode 3 has the shape of a fiat frame and protrudes beyondthe surface of the cathode. The direction of vision is indicated by the arrow 4 as seen from Fig. 2. In order to mount'the electrodes 2 and 3 in a definite and fixed position with respect to each other, different means, may be used, as is well known in the art. Thus, for instance, glass rods may be disposed at both sides which serve for supporting the electrodes, or the electrodes may be sealed into supporting members connected to the glass wall of the tube. The tube itself may be filled with any one of the well-known gases, such as neon, helium, etc., at suitable.

pressure, such as is well known in the art.

- Referring to the cathode electrode, it has been customary to use an entirely rough and unfinished material, or to use a cathode which has been specially roughened as by means of a sand blast. In accordance with our invention we use a cathode whose entire surface, or at least a portion of it constituting the field of vision such as circumscribed by the anode frame, has been polished to high brilliancy. With this, we have found that a number of advantageous effects are obtained. Primarily, the radiation of the light in the direction of vision is increased as all the rays transmitted from the glowing layer upon the cathode are reflected from the same and directed to the 'eye of the observer. Furthermore, we have found that the glow discharge on polished surfaces maintains a high stability even with comparatively very low density of operating current, whereas with the glow discharge tubes as hitherto used in the art very early a jumping and moving about of the glowing layer takes place. This latter effect is of primary importance in television, whereit is necessary that the field of vision must be covered with uniform 'to use a material for the cathode which in a and stable luminescence in order to production of a clear picture.

- Further advantages of a polished surface, especially when steel is used as a cathode material, consist in a low cathode drop and a large decrease of cathode disintegration. These latter efiects may be explained principally in that both the bombardment of ions and the emission of electrons take place completelyat right angles insure a the to the cathode when using a polished surface,

whereas when using the customary rough or metal surfaces field distortions in the immediate neighborhood of the 'cathode will take place which react in a disturbing manner on the proces of liberation of the electrons and which will have a favorable reaction on the mechanical part of the disintegration and erosive process. v

In order to insure an improved reflection of the blue rays which, as is well known, are produced in a very weak degree only in the customary television lamps, it has been found suitable state of high polish is of white or blue-white appearance. We have found thatof the mate'- rials to be used for this purpose (silver, magnesium alloys,.cliromium, 'etc.) chromium is the mostsuitableand produces the most favorable appearance on account of its extraordinarily low ing such as by an electrolytic process, and then 5 polished.

Especially favorable results, in accordance with the present invention, may be obtained by using a. mirrored cathode surface of a carbon containing material, such as for instance of a highly polished steel, primarily silver steel. We have found that the glowing layer produced on such cathodes assumes a very white color which, as pointed out, is of special importance for purposes of television. This favorable phenomenon It may have its explanation in the action of the carbon particles on the glow discharge which have been set free by the polishing process.

Referring to Fig. 3, we have shown a complete television system in a schematic manner in which 20 a. glow lamp of. the type as described may be utilized. An object 8 at the transmitter is scanned by means of a rotating spiral disc 6 in the usual manner through a pencil of light produced by a source 9 passingthrough lenses l0 and Hand 25 the holes of the scanning disc. The light rays reflected from the object act on a photoelectric cell l2 which is connected in a suitable circuit system for producing corresponding electric current variations to be amplified by an amplifier l3 and'BO to be transmitted through a line l5 or other medium of transmission to the receiving station. At the latter a scanning disc 1 similar to the transmitter scanning disc 6 is provided which, in a well-known manner, runs synchronously with the transmitter-disc.- We have not shown the means for securing synchronization of both transmitting and scanning discs as these are well known in the art and are outside the scope of the present invention. The incoming current variations are 40 amplified by an amplifier l4 and then applied to the anode 3 and cathode 2 of the receiving glow lamp I, as illustrated. By looking in the direction of the arrow 4 against the receiving disc beyond which the receiving lamp 1 is disposed, a picture of the object 8 at the transmitter is viewed. For this purpose it is necessary, providing that there is complete synchronism between transmitting disc 6 and receiving disc 1, that the size of the image, that is, the height of the opening of the anode frame, is equal to the difference of the diameter of the outermost hole 01. the

scanning disc from the diameter of the innermost hole- Furthermore, it is necessary,- as is well known, that the spacing of the spiral holes 5 from each other is such that onehole has passed the complete width of the image frame when the succeeding hole begins to pass over the following horizontal line of the image.

While we have shown our invention in a preferred form, it is obvious that many changes may be made in the details of construction and embodiment thereof without departing from the principle and spirit of the invention. We desire,

therefore, that thecappended claims shall be accorded the broadest construction commensurate with the language thereof when read in the light of. the prior art.

What we claim as new and useful and desire to secure by Letters Patent is:- 70

1. In a glow discharge lamp comprising a vessel containing a gaseous atmosphere, a fiat catho de electrode within said vessel having a mirrored operating glowing surface, and a flat frame-like anode disposed opposite said mirrored surface and aormvs 3 yond the edges of said cathode for fencing off a desired viewing field covering substantially the entire cathode surface. v

3. 4 glow discharge lamp comprising a vessel containing a gaseous at osphere, a cathode electrode within said vessel h ving. a highly polished chromiumsurfaceon whi I be produced, and an anode electrode cooperating with said cathode.

4. In a glow lamp for receiving television pictures, comprising a vessel containing a gaseous atmosphere, a highly polished plate-like cathode electrode consisting of chromium, and a framelike anode electrode disposed opposite said cathode and circumscribing the desired viewing field upon said cathode.

5.- In a glow lamp for receiving television pictures, comprising a vessel containing a gaseous atmosphere, a fiat cathode having a highly p01 ished chromium surface within said vessel, and a frame-like anode disposed opposite said polished surface of said cathode circumscribing the desired'field of vision upon said cathode and having its edges protruding beyond the edges of said cathode. I

6. In an electric glow discharge lamp comprising avessel containing a gaseous atmosphere; it

plate-like cathode electrode within said vessel having a mirrored surface and an anode having the shape of a fiat frame disposed opposite and parallel to said mirrored surface and circumscribing the desired viewing'field covering substantially the entire cathode surface.

. '7. In an electric glow discharge lamp comprising a vessel containing a gaseous atmosphere; a

flat cathode electrode within said vessel having a a glowing layer is to.

mirrored surface: an anode having the shape of a fiat frame disposed opposite and parallel to'said mirrored surface of said cathode and circumscribing the desired viewing field on said cathode covering substantially the entire cathode surface,

said anode frame having its edges protruding beyond the edges of said cathode electrode.

8. A glow discharge lamp comprising a vessel containing a gaseous atmosphere; a plate-like cathode electrode within said vessel; and an anode 10 disposed opposite said cathode and having the shape of a hat frame parallel to said cathode fencing off the viewing field covering substantially the entire cathode surface.

9. An electric glow discharge lamp comprising a vessel containing a gaseous atmosphere; a fiat cathode electrode within said vessel; anda cooperating anode electrode having the shape of a fiat frame and disposed opposite and parallel to said cathode to fence off a desired viewing field covering substantially the entire cathode surface, the outer edges of said anode frame protruding lie-1 v yond the edges of said cathode.

10. In an electric glow discharge lamp for receiving television pictures comprising. a vessel containing a gaseous atmosphere; a highly polished fiat cathode electrode consisting of chromium and a cooperating anode electrode having the shape of a flat frame disposed opposite and parallel to said cathode and circumscribing. the desired viewing 8. field upon said cathode.

11. In an electric glow discharge lamp for receiving television pictures comprising a vessel containing a gaseous atmosphere; .a flat cathode having a highly polished chromium surface within said vessel; a cooperating anode electrode having the shape of a fiat frame disposed opposite and parallel to said polished surface and circumscribing the desired viewing field upon said cathode, the outer edges 'of said anode frame protrud- 4 0' ing beyond the edges of said cathode.

' HEINRICH H. GEFFCKEN. HANS R. RICHTER. 

